The present invention relates to an optical encoder and electronic equipment having the same. More particularly, the present invention relates to an optical encoder using light-receiving devices to detect locations, moving velocities and moving directions of mobile objects.
As a first conventional optical encoder, there is one, as disclosed in JP H2000-193492 A, which includes a light-emitting device for emitting light toward a mobile object and a light-receiving device for receiving light passing through the mobile object, wherein current to the light-emitting device is rectified based on signals outputted from the light-receiving device to automatically correct the amount of emitted light in the light-emitting device.
As a second conventional optical encoder, there is one, as disclosed in JP 2003-65802 A, which includes a plurality of light-emitting devices, a mobile object having a slit portion through which light emitted from the light-emitting devices passes, and a plurality of light-receiving devices for receiving the light, wherein a plurality of light-emitting devices are driven to emit light in time-sharing sequential cycles and information on movement of the mobile object (hereinbelow referred to as “movement information on the mobile object”) is detected based only on the light-receiving signal from the light-receiving device corresponding to the light-emitting device which is currently emitting light.
In the first and second conventional optical encoders, power consumption mainly occurs in the light-emitting devices. In the first conventional optical encoder, during velocity detection of the mobile object, the light-emitting device is always in the ON state. In the second conventional optical encoder, one of a plurality of the light-emitting devices is always in the ON state. Therefore, both the first and second conventional optical encoders have such problem as large power consumption.
Further, in the first and second optical encoders, particularly in the case where LEDs (Light Emitting Diodes) with wide directivity are used as the light-emitting devices or in the case where the optical encoders are downsized, incidence of parallel light into the light-receiving devices becomes difficult, thereby making variation in light reception larger and making it difficult to obtain accurate movement information on the mobile object. Also in the second encoder, incidence of parallel light into the light-receiving device is difficult because the property of the respective LEDS remains unchanged, and also there are other factors such as refraction of light in the slit of the mobile object.